Recently, global warming is pointed out associated with the increase of carbon dioxide emission, which is a significant issue even in the iron industry. As to such an issue, an operation with a low reduction agent ratio (total amount of a reducing material blown through tuyeres and coke charged from a top of the furnace per 1 ton of pig iron to be produced) is driven forward in recent blast furnaces. In the blast furnace, coke and pulverized coal are mainly used as a reducing material. Therefore, in order to attain the operation with a low reduction agent ratio and hence the suppression of carbon dioxide emission, it is effective to replace coke or the like with a reducing material having a high hydrogen content ratio such as waste plastic, LNG, heavy oil or the like.
Patent Document 1 discloses a method wherein the reduction agent ratio is decreased by using a plurality of lances and blowing a solid reducing material, a gaseous reducing material and a combustible gas through the respective lances to promote the heating of the solid reducing material to thereby improve the combustion efficiency and hence suppress the generation of unburned powder or coke breeze for improving air permeability. Patent Document 2 discloses a technique wherein coaxially multiple-tube type lances are used and a combustible gas is blown through an inner tube and a gaseous reducing material and a solid reducing material are blown from a gap between inner tube and outer tube. Patent Document 3 proposes a lance wherein plural small-size tubes are arranged in parallel around a main lance tube. Patent Document 4 discloses multiple nozzles in which plural blowing tubes are arranged in parallel at interval outside a fuel feeding tube when a combustible gas and a fuel are blown into a smelting reduction furnace, whereby a mixed state of the combustible gas and the fuel can be always maintained even if one of the nozzles is wear-damaged.